Processes for recovering rare earth elements from various ores

ABSTRACT

The present disclosure relates to processes for recovering rare earth elements from various materials. The processes can comprise leaching the at least one material with at least one acid so as to obtain a leachate comprising at least one metal ion and at least one rare earth element, and a solid, and separating the leachate from the solid. The processes can also comprise substantially selectively removing at least one of the at least one metal ion from the leachate and optionally obtaining a precipitate. The processes can also comprise substantially selectively removing the at least one rare earth element from the leachate and/or the precipitate.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a 35 USC 371 national stage entry ofPCT/CA2012/000419 filed on May 3, 2012 and which claims priority on U.S.61/482,253 filed on May 4, 2011; on U.S. 61/535,435 filed on Sep. 16,2011 and on PCT/CA2012/000253 filed on Mar. 19, 2012. These documentsare hereby incorporated by reference in their entirety.

TECHNICAL FIELD

The present disclosure relates to improvements in the field of chemistryapplied to the recovery, extraction and/or isolation of rare earthelements (REE). For example, such processes are useful for obtainingrare earth elements from various materials and derivatives thereof suchas aluminum-bearing materials and derivatives, zinc-bearing materialsand derivatives thereof, copper-bearing materials and derivativesthereof, nickel-bearing materials and derivatives thereof, andtitanium-bearing materials and derivatives thereof.

BACKGROUND OF THE DISCLOSURE

In various technologies, there is an increasing need for rare earthelements. In few countries, efforts to reestablish mining of rare earthelements have been undertaken. In the future, supplies of rare earthelements will considerably depend upon economic viability of theextraction and production processes and technological innovationsrequiring such rare earth elements.

There is thus a need for providing an alternative to the existingsolutions for extracting rare earth elements.

SUMMARY OF THE DISCLOSURE

According to one aspect, there is provided a process for recovering atleast one rare earth element from at least one material, the processcomprising:

-   -   leaching the at least one material with at least one acid so as        to obtain a leachate comprising at least one metal ion, and the        at least one rare earth element;    -   substantially selectively precipitating, extracting and/or        isolating the at least one metal ion from the leachate and        optionally obtaining a precipitate; and    -   substantially selectively precipitating, extracting and/or        isolating the at least one rare earth element from the leachate        and/or the precipitate.

According to one aspect, there is provided a process for extracting atleast one rare earth element from at least one material, the processcomprising:

-   -   leaching the at least one material with at least one acid so as        to obtain a leachate comprising at least one metal ion, and the        at least one rare earth element; and    -   selectively precipitating at least one member chosen from the at        least one rare earth element, and the at least one metal ion.

According to one aspect, there is provided a process for recovering atleast one rare earth element from at least one material, the processcomprising:

-   -   leaching the at least one material with at least one acid so as        to obtain a leachate comprising at least one metal ion, and at        least one rare earth element;    -   optionally substantially selectively precipitating, extracting        and/or isolating the at least one rare earth element from the        leachate and/or the precipitate.    -   substantially selectively precipitating, extracting and/or        isolating the at least one metal ion from the leachate and        optionally obtaining a precipitate; and    -   substantially selectively precipitating, extracting and/or        isolating the at least one rare earth element from the leachate        and/or the precipitate.

According to another example, there is provided a process for recoveringat least one rare earth element from at least one material, the processcomprising:

-   -   leaching the at least one material with at least one acid so as        to obtain a leachate comprising at least one metal ion, the at        least one rare earth element, and a solid, and separating the        leachate from the solid;    -   substantially selectively removing at least one metal ion from        the leachate and optionally obtaining a precipitate; and    -   substantially selectively removing the at least one rare earth        element from the leachate and/or the precipitate.

According to another example, there is provided process for recoveringat least one rare earth element from at least one material, the processcomprising:

-   -   leaching the at least one material with at least one acid so as        to obtain a leachate comprising at least one metal ion and the        at least one rare earth element, and a solid, and separating the        leachate from the solid; and    -   substantially selectively removing at least one member chosen        from the at least one rare earth element and the at least one        metal ion from the leachate.

BRIEF DESCRIPTION OF DRAWINGS

In the following drawings, which represent by way of example only,various embodiments of the disclosure:

FIG. 1 shows a bloc diagram of an example of a process for preparingalumina and various other products including rare earth elements,according to the present disclosure;

FIG. 2 shows a bloc diagram of another example of process for preparingalumina and various other products including rare earth elements,according to the present disclosure;

FIG. 3 shows a bloc diagram of an example of process for extracting rareearth elements according to the present disclosure; and

FIGS. 4a and 4b show a bloc diagram of another example of a process forextracting rare earth elements according to the present disclosure.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS

Further features and advantages will become more readily apparent fromthe following description of various embodiments as illustrated by wayof examples.

It was found that that the rare earth element(s) recovery can be made,for example, in the processes described in the present disclosure atvarious stages. Moreover, it was found that such processes can be usefuleven if the rare earth elements are only found as traces. It was alsofound that such processes can be particularly useful for extracting rareearth elements from a solution that is substantially refined orpurified. For example, these processes can be useful since they can beapplied to solutions from which several of the main components have beenremoved They can also be applied to solutions before removal of severalof the main components.

The expression “at least one aluminum ion”, as used herein refers, forexample, to at least one type of aluminum ion chosen from all possibleforms of Al ions. For example, the at least one aluminum ion can beAl³⁺.

The expression “at least one iron ion”, as used herein refers, forexample, to at least one type of iron ion chosen from all possible formsof Fe ions. For example, the at least one iron ion can be Fe²⁺, Fe³⁺, ora mixture thereof.

The expression “at least one zinc ion”, as used herein refers, forexample, to at least one type of zinc ion chosen from all possible formsof Zn ions. For example, the at least one zinc ion can be Zn²⁺.

The expression “at least one copper ion”, as used herein refers, forexample, to at least one type of copper ion chosen from all possibleforms of Cu ions. For example, the at least one copper ion can be Cu¹⁺or Cu²⁺, or a mixture thereof.

The expression “at least one nickel ion”, as used herein refers, forexample, to at least one type of nickel ion chosen from all possibleforms of Ni ions. For example, the at least one nickel ion can be Ni²⁺or Ni³⁺, or a mixture thereof.

The expression “at least one titanium ion”, as used herein refers, forexample, to at least one type of titanium ion chosen from all possibleforms of Ti ions. For example, the at least one titanium ion can be Ti³⁺or Ti⁴⁺, or a mixture thereof.

The expression “at least one rare earth element”, as used herein refers,for example, to at least one type of rare earth element chosen from allthe rare earth elements described in the present disclosure in all theirpossible forms.

The expression “Ga-free solution”, as used herein refers, for example,to a solution that comprises about less than 5%, 2% or 1% w/v ofgallium.

The expression “Ce-free solution”, as used herein refers, for example,to a solution that comprises about less than 5%, 2% or 1% w/v of cerium.

The expression “Sc-free solution”, as used herein refers, for example,to a solution that comprises about less than 5%, 2% or 1% w/v ofscandium.

The expression “Sm-free solution”, as used herein refers, for example,to a solution that comprises about less than 5%, 2% or 1% w/v ofsamarium.

The expression “Eu-free solution”, as used herein refers, for example,to a solution that comprises about less than 5%, 2% or 1% w/v ofeuropium.

The expression “Gd-free solution”, as used herein refers, for example,to a solution that comprises about less than 5%, 2% or 1% w/v ofgadolinium.

The expression “Y-free solution”, as used herein refers, for example, toa solution that comprises about less than 5%, 2% or 1% w/v of yttrium.

The expression “Pr-free solution”, as used herein refers, for example,to a solution that comprises about less than 5%, 2% or 1% w/v ofpraseodymium.

The expression “Nd-free solution”, as used herein refers, for example,to a solution that comprises about less than 5%, 2% or 1% w/v ofneodymium.

The expression “La-free solution”, as used herein refers, for example,to a solution that comprises about less than 5%, 2% or 1% w/v oflanthanum.

The expression “Er-free solution”, as used herein refers, for example,to a solution that comprises about less than 5%, 2% or 1% w/v of erbium.

The expression “Dy-free solution”, as used herein refers, for example,to a solution that comprises about less than 5%, 2% or 1% w/v ofdysprosium.

The expression “rare earth element” as used herein refers, for example,to a rare element chosen from scandium, yttrium, lanthanum, cerium,praseodymium, neodymium, promethium, samarium, europium, gadolinium,terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium,and/or a rare metal chosen from indium, zirconium, lithium, and gallium.These rare earth elements and rare metals can be in various form such asthe elemental form (or metallic form), under the form of chlorides,oxides, hydroxides etc.

The expression “the at least one rare earth element” as used hereinrefers, for example, to a at least one rare element chosen fromscandium, yttrium, lanthanum, cerium, praseodymium, neodymium,promethium, samarium, europium, gadolinium, terbium, dysprosium,holmium, erbium, thulium, ytterbium, and lutetium, and/or to at leastone rare metal chosen from indium, zirconium, lithium, and gallium.These rare earth elements and rare metals can be in various form such asthe elemental form (or metallic form), or under the form of chlorides,oxides, hydroxides etc.

In the processes of the present disclosure, after the leaching, thesubstantially selectively removing of the at least one member chosenfrom the at least one rare earth element and the at least one metal fromthe leachate can be made in various manners. The at least one metal ion(or a second metal ion) can be removed and then, a first metal ion canbe removed and finally, the at least one rare earth element can beremoved. Alternatively, the first metal ion can be removed, then thesecond metal ion can be removed and finally, the at least one rare earthelement can be removed. According to another example, the at least onerare earth element can be removed, then, the first metal ion can beremoved, and finally the second metal ion can be removed. Also, the atleast one rare earth element can be removed, then, the second metal ioncan be removed, and finally the first metal ion can be removed. Variousother possible combinations can also be envisaged.

The at least one acid used for leaching the at least one material can beHCl, H₂SO₄, HNO₃ or mixtures thereof. More than one acid can be used asa mixture or separately. Solutions made with these acids can be used atvarious concentration. For example, concentrated solutions can be used.For example, 6 M or 12 M HCl can be used. For example, up to 98% or 100%wt H₂SO₄ can be used.

For example, the at least one material can be leached with HCl having aconcentration of about 15 to about 45 weight %, of about 20 to about 45weight %, of about 25 to about 45 weight %, of about 26 to about 42weight %, of about 28 to about 40 weight %, of about 30 to about 38weight %, or between 25 and 36 weight %.

For example, the at least one material can be leached at a temperatureof about 125 to about 225° C., about 150 to about 200° C., about 160 toabout 180° C., or about 165 to about 170° C.

For example, the leaching can be carried out under pressure. Forexample, the pressure can be about 100 to about 300 or about 150 toabout 200 psig. The leaching can be carried out for about 30 minutes toabout 5 hours. For example, the leaching can be carried out at atemperature of about 60° C. to about 200° C.

For example, the leaching can be carried out under pressure into anautoclave. For example, it can be carried out at a pressure of 5 KPag toabout 850 KPag, 50 KPag to about 800 KPag, 100 KPag to about 750 KPag,150 KPag to about 700 KPag, 200 KPag to about 600 KPag, or 250 KPag toabout 500 KPag.

For example, the leaching can be carried out at a temperature of atleast 80° C., at least 90° C., or about 100° C. to about 110° C. Incertain cases it can be done at higher temperatures so as to increaseextraction yields of rare earth elements in certain ores. For example,the leaching can be carried out at a temperature of at least 100° C., atleast 120° C., at least 130° C., at least 140° C., or about 140° C. toabout 175° C.

For example, in the leachate, the at least one rare earth element can bein the form of an ion.

For example, after the leaching, the at least one rare earth element canbe solubilized into the solution and can be found as a soluble ion,associated to chlorine, a sulfate, a nitrate, or hydrates thereof. etc.

For example, after the leaching, (if required) various bases can be usedfor raising up the pH such as KOH, NaOH, Ca(OH)₂, CaO, MgO, Mg(OH)₂,CaCO₃, Na₂CO₃, NaHCO₃, CO₂, or mixtures thereof.

For example, the at least one material can be chosen fromaluminum-bearing materials and derivatives, zinc-bearing materials andderivatives thereof, copper-bearing materials and derivatives thereof,nickel-bearing materials and derivatives thereof, and titanium-bearingmaterials and derivatives thereof.

For example, the at least one metal ion can comprise at least onealuminum ion, at least one zinc ion, at least one copper ion, at leastone nickel ion, at least one titanium ion and/or at least one iron ion.

For example, the at least one metal ion can comprise a first metal ionand a second metal ion.

For example, the first metal ion can comprise at least one aluminum ion,at least one zinc ion, at least one copper ion, at least one nickel ion,at least one titanium ion and/or at least one iron ion.

For example, the second metal ion can comprise at least one aluminumion, at least one zinc ion, at least one copper ion, at least one nickelion, at least one titanium ion and/or at least one iron ion.

For example, the first metal ion can be at least one aluminum ion.

For example, the second metal ion can be at least one iron ion.

For example, the at least one iron ion can be precipitated. Whenprecipitating the at least one iron ion, it can be precipitated by meansof an ionic precipitation and it can precipitate in the form of varioussalts, hydroxides, chlorides or hydrates thereof. For example, the atleast one iron ion can be precipitated as FeCl₂, FeCl₃, Fe(OH)₃,Fe(OH)₂, hematite, geotite, jarosite or hydrates thereof.

For example, after the precipitation of the at least one iron ion, theat least one rare earth element can be solubilized into the solution andcan be found as a soluble ion, associated as an hydroxide or a salt, orhydrates thereof.

For example, the at least aluminum ion can be precipitated. Whenprecipitating the at least aluminum ion, it can be precipitated by meansof an ionic precipitation and it can precipitate in the form of varioussalts, (such as chlorides, sulfates) or hydroxides or hydrates thereof.For example, the at least one aluminum ion can be precipitated asAl(OH)₃, AlCl₃, Al₂(SO₄)₃, or hydrates thereof.

For example, after the precipitation of the at least one metal ion, theat least one rare earth element can be solubilized into the solution andcan be found as a an ion associated to an hydroxide or a salt orhydrates thereof.

For example, after precipitation of the at least one metal ion, theresidual and substantially purified or refined solution can contain theat least one rare earth element into a mixture of residual soluble ions,such as Cl⁻, SO₄ ²⁻, Na⁺.

The processes of the present disclosure can be effective for treatingvarious materials. The at least one material can be an aluminum-bearingmaterial, The aluminum-bearing material can be an aluminum-bearing ore.For example, clays, argillite, mudstone, beryl, cryolite, garnet,spinel, bauxite, or mixtures thereof can be used as starting material.The aluminum-bearing material can also be a recycled industrialaluminum-bearing material such as slag. The aluminum-bearing materialcan also be red mud.

The processes of the present disclosure can be effective for treatingvarious nickel-bearing ores. For example, niccolite, kamacite, taenite,limonite, garnierite, laterite, pentlandite, or mixtures thereof can beused.

The processes of the present disclosure can be effective for treatingvarious zinc-bearing ores. For example, smithsonite, warikahnite,sphalerite, or mixtures thereof can be used.

The processes of the present disclosure can be effective for treatingvarious copper-bearing ores. For example, copper-bearing oxide ores, canbe used. For example, chalcopyrite, chalcocite, covellite, bornite,tetrahedrite, malachite, azurite, cuprite, chrysocolla, or mixturesthereof can also be used.

The processes of the present disclosure can be effective for treatingvarious titanium-bearing ores. For example, ecandrewsite, geikielite,pyrophanite, ilmenite, or mixtures thereof can be used.

For example, the at least one rare earth element can be chosen fromscandium, yttrium, lanthanum, cerium, praseodymium, neodymium,promethium, samarium, europium, gadolinium, terbium, dysprosium,holmium, erbium, thulium, ytterbium, and lutetium, and from at least onerare metal chosen from indium, zirconium, lithium, and gallium.

For example, rare earth elements can sometimes be divided into twocategories, light rare earth elements (LRE) and heavy rare earthelements (HRE). The light rare earth elements can comprise lanthanum,cerium, praseodymium, neodymium, and samarium (atomic numbers 57-62),and they are usually more abundant than heavy ones.

For example, the at least one rare element can be extracted under theform of various salts, oxides, hydroxides, and hydrates thereof.

For example, the at least one rare earth element can be chosen fromscandium, gallium, yttrium, lanthanum, cerium, praseodymium, neodymium,promethium, samarium, europium, gadolinium, dysprosium, erbium,ytterbium and mixtures thereof.

For example, the at least one rare earth element is chosen fromscandium, gallium, yttrium, lanthanum, cerium, praseodymium, neodymium,promethium, samarium, europium, gadolinium, dysprosium and mixturesthereof.

For example, the at least one rare earth element is chosen fromscandium, gallium, yttrium, cerium and mixtures thereof.

For example, the at least one rare earth element can be yttrium.

For example, the at least one rare earth element can be scandium.

For example, the at least one rare earth element can be gallium.

For example, the at least one rare earth element can be cerium.

For example, the processes can comprise:

-   -   leaching the at least one material with HCl so as to obtain the        leachate comprising the at least one metal ion, and the at least        one rare earth element, and the solid and separating the        leachate from the solid;    -   substantially selectively removing the at least one metal ion        from the leachate, thereby obtaining a composition comprising        the metal ion, and the at least one rare earth element; and    -   substantially selectively at least partially removing the at        least one metal ion from the composition, thereby obtaining a        liquor comprising the at least one rare earth element.

For example, the at least one metal ion can be substantially selectivelyremoved from the leachate by substantially selectively precipitating itfrom the leachate and removing it therefrom by carrying out asolid-liquid separation.

For example, the at least one metal ion can be substantially selectivelyremoved from the leachate by substantially selectively precipitating itunder the form of AlCl₃ and removing it therefrom by carrying out asolid-liquid separation.

For example, the composition can comprise HCl, the at least one metalion, and the at least one rare earth element.

For example, the composition can be an acidic composition thatcomprises, the at least one metal ion, and the at least one rare earthelement.

For example, the at least one iron ion can be substantially selectivelyremoved from the composition by carrying out an hydrolysis so as toconvert the at least one iron ion into Fe₂O₃ and removing theprecipitated Fe₂O₃ from the composition by carrying out a solid-liquidseparation, thereby obtaining the liquor comprising the at least onerare earth element.

For example, after the removal of the precipitated Fe₂O₃, the liquorcontaining the at least one rare earth element is recirculated back forbeing further concentrated by being used in precipitating the at leastone aluminum ion.

For example, after the removal of the precipitated Fe₂O₃, the liquorcontaining the at least one rare earth element is recirculated back forbeing further concentrated by being used in precipitating the at leastone aluminum ion under the form of AlCl₃.

For example, the at least one iron ion can be Fe³⁺ and it can besubstantially selectively partially removed from the composition, andwherein the composition can be further treated with a reducing agent soas to convert Fe³⁺ into Fe²⁺ and then, Fe²⁺, under the form of FeCl₂,can be removed from the composition by carrying out a solid-liquidseparation, thereby obtaining the liquor comprising the at least onerare earth element.

For example, the at least one rare earth element can be substantiallyselectively precipitated, extracted and/or isolated from the liquor bymeans of a liquid-liquid extraction.

For example, the at least one rare earth element can be extracted fromthe liquor by means of liquid-liquid extraction.

For example, the at least one rare earth element can be recovered fromthe liquor by means of liquid-liquid extraction.

For example, the at least one extracting agent can be chosen fromdi-(2-ethylhexyl) phosphoric acid (HDEHP),mono(2-ethylhexyl)2-ethylhexyl phosphonate (HEH/EHP),bis(2,4,4-trimethylpentyl)monothiophosphinic acid), octyl phenylphosphate (OPAP), 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester(PC88A) and optionally toluene, tributyl phosphate, di-isoamylmethylphosphonate, 7-(4-ethyl-1-methyloctyl)-8-hydroxyquinoline,di-(2-ethylhexyl) phosphinic acid, bis(2,4,4-trimethylpentyl) phosphinicacid, 8-hydroxyquinoline, and (2-ethylhexyl)phosphonic acid, andmixtures thereof.

For example, the at least one extracting agent can be di-(2-ethylhexyl)phosphoric acid.

For example, the at least one extracting agent can be2-ethylhexylphosphonic acid mono-2-ethylhexyl ester.

For example, the at least one extracting agent can be octyl phenylphosphate.

For example, the at least one extracting agent can be tributylphosphate.

For example, the at least one extracting agent can be chosen fromdiethylenetriamine-penthaacetic acid (DTPA), ethylenediaminetetraacetic(EDTA), 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA),bis(2,4,4-trimethylpentyl)monothiophosphinic acid and mixtures thereof.

According to one example, when substantially selectively precipitating,extracting and/or isolating the at least one rare earth element from theleachate and/or the precipitate, the at least one rare earth elementfound as an ion in the leachate can be precipitated.

For example, scandium can be precipitated in the form of Sc(OH)₃, ScCl₃,ScF₃, and/or [ScF₆]³⁻ (cation), wherein the cation can be sodium,potassium, magnesium, calcium etc

Scandium can be precipitated at a pH of about 7 to about 9, or about 7to about 8.

For example, the leaching can be carried out at a pH of about 0.5 toabout 2.5, about 0.5 to about 1.5, or about 1; then the second metal ioncan be precipitated at a pH of at least about 9.5, 10, 10.5, 11, or11.5; and then the first metal ion can be precipitated at a pH of about8 to about 9.

For example, the second metal ion can be precipitated at a pH of about10 to about 12.5, 10.5 to about 11.5, about 10.8 to about 11.2, about11.5 to about 12.5, or between 10 and 11.

For example, the precipitation of the first metal ion can be carried outat a pH of about 7 to about 11, about 8 to about 10.5, about 8.5 to 10or about 9 to about 10.

For example, the precipitation of the second metal ion can be carriedout at a pH of about 3 to about 6, about 3.0 to about 5.5, about 3 toabout 5, about 3 to about 4, about 3.0 to about 3.5, about 3.5 to about4.0, about 4.0 to about 5.0, about 4.0 to about 4.5, or about 4.5 toabout 5.0.

For example, the precipitation of the first metal ion can be carried outat a pH of about 5 to about 6, about 5.0 to about 5.5, or about 5.5 toabout 6.0.

For example, when precipitating AlCl₃, highly concentrated dry gaseousHCl at about 90 to about 98% can be bubbled into the compositioncomprising the at least one iron ion, the at least one aluminum ion andthe at least one rare earth element.

For example, when carrying out the hydrolysis of the at least one ironion so as to convert the at least one iron ion into Fe₂O₃ and removingthe Fe₂O₃, the pH during the hydrolysis can be about below 2.5, 2.0, 1.5or 1.0.

According to another example, the liquor can comprise the at least onerare earth element under the form of a chloride, and wherein the liquorcan be reacted with an extracting agent in order to substantiallyselectively extract gallium therefrom, thereby obtaining a Ga-freesolution and an extracted gallium solution, and separating the solutionsfrom one another. For example, gallium in the liquor can be under theform of GaCl₃. For example, the extracting agent can be octyl phenylphosphate, 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester andtoluene, tri-butyl phosphate or mixtures thereof. For example, theextracted GaCl₃ can then be precipitated and then converted into Ga₂O₃.

For example, the Ga-free solution can then be reacted with another anextracting agent in order to substantially selectively extract ceriumtherefrom, thereby obtaining a Ce-free solution and an extracted ceriumsolution, and separating the solutions from one another. For example,the cerium in the Ga-free solution can be under the form of CeCl₃. Forexample, the another extracting agent can be tri-butyl phosphate,di-isoamylmethyl phosphonate, di-(2-ethylhexyl) phosphoric acid,7-(4-ethyl-1-methyloctyl)-8-hydroxyquinoline or mixtures thereof. Forexample, the process can further comprise converting the extractedcerium into CeO₂.

For example, the process can further comprise reacting the Ce-freesolution with a further extracting agent in order to substantiallyselectively extract scandium therefrom, thereby obtaining a Sc-freesolution and an extracted scandium solution, and separating thesolutions from one another. For example, scandium in the Ce-freesolution can be under the form of ScCl₃. For example, the furtherextracting agent can be di-(2-ethylhexyl) phosphoric acid,di-(2-ethylhexyl) phosphinic acid or a mixture thereof. For example, theprocess can further comprise converting the extracted scandium intoSc₂O₃. For example the extracted scandium can be converted into Sc₂O₃ bymeans of NaOH.

For example, the process can further comprise reacting the Sc-freesolution with still a further extracting agent in order to substantiallyselectively extract samarium, europium or a mixture thereof, therebyobtaining a Sm-free solution and/or Eu-free solution and extractedsamarium and/or europium solution, and separating the solutions from oneanother. For example, the still a further extracting agent can be chosenfrom bis(2,4,4-trimethylpentyl) phosphinic acid, di-(2-ethylhexyl)phosphoric acid and a mixture thereof.

For example, the process can further comprise reacting the Sm-freesolution and/or Eu-free solution with still another extracting agent inorder to substantially selectively extract gadolinium, thereby obtaininga Gd-free solution and an extracted gadolinium solution, and separatingthe solutions from one another. For example, the still anotherextracting agent can be 8-hydroxyquinoline.

For example, the process can further comprise reacting the Gd-freesolution with yet another extracting agent in order to substantiallyselectively extract yttrium, thereby obtaining a Y-free solution and anextracted yttrium solution, and separating the solutions from oneanother. For example, the yet another extracting agent can be(2-ethylhexyl)phosphonic acid, di-(2-ethylhexyl)phosphonic acid or amixture thereof.

For example, the process can further comprise reacting the Y-freesolution with still yet another extracting agent in order tosubstantially selectively extract dysprosium and/or erbium, therebyobtaining a Dy-free solution and/or an Er-free solution and an extracteddysprosium and/or erbium solution, and separating the solutions from oneanother.

According to another example, the liquor can be reacted with a firstextracting agent in order to substantially selectively extract galliumtherefrom, thereby obtaining a Ga-free solution and an extracted galliumsolution, and separating the solutions from one another.

For example, gallium in the liquor can be under the form of GaCl₃. Forexample, the first extracting agent can be tri-butyl phosphateoptionally in kerosene.

For example, the Ga-free solution can be reacted with a precipitatingagent for precipitating at least one rare earth element present in theGa-free solution, thereby obtaining a precipitate containing the atleast one rare earth element and recovering the precipitate via asolid-liquid separation.

For example, the process can further comprise leaching the precipitatewith at least one acid so as to obtain a leach solution comprising theat least one rare earth element. For example the acid can be HCl. Forexample, the leach solution can be reacted with a second extractingagent so as to substantially selectively extract a first group of rareearth elements, thereby obtaining a solution comprising the extractedrare earth elements of the first group and a raffinate comprising asecond group of rare earth elements, and separating the solution fromthe raffinate. For example, the first group can comprise yttrium andscandium. For example, the second group can comprise cerium, neodynium,europium and praseodymium. For example, the second extracting agent canbe chosen from di-(2-ethylhexyl)phosphoric acid and2-ethylhexylphosphonic acid mono-2-ethylhexyl ester.

For example, the process can further comprise reacting the solutioncomprising the extracted rare earth elements of the first group with HClat least once so as to remove impurities therefrom.

For example, the process can further comprise stripping the solutioncomprising the extracted rare earth elements of the first group with atleast one acid so as to obtain a first group strip liquor. For example,the at least one acid can be HCl.

For example, the process can further comprise repeating at least oncethe extraction with the second extracting agent.

For example, the first group strip liquor can be reacted with a thirdextracting agent so as to substantially selectively extracting at leastone of scandium, erbium and dysprosium from the first group stripliquor, thereby obtaining a solution comprising the extracted at leastone of scandium, erbium and dysprosium, and an yttrium raffinate, andseparating the solution from the raffinate. For example, the thirdextracting agent can be tri-butyl phosphate.

For example, the process can further comprise stripping the solutioncomprising the extracted at least one of scandium, erbium and dysprosiumsolution with at least one acid so as to obtain another first groupstrip liquor. For example, the at least one acid can be HCl.

For example, the another first group strip liquor can be reacted with afourth extracting agent so as to substantially selectively extractingerbium and dysprosium from the another first group strip liquor, therebyobtaining a solution comprising the extracted erbium and dysprosium, anda scandium raffinate, and separating the solution from the raffinate.

For example, the another first group strip liquor can be reacted with afourth extracting agent so as to substantially selectively extractingscandium from the another first group strip liquor, thereby obtaining asolution comprising the extracted scandium, and raffinate comprisingerbium and dysprosium, and separating the solution from the raffinate.

For example, the at least one rare earth element can be substantiallyselectively precipitated, extracted and/or isolated by means of anadsorption on activated charcoal optionally modified with tributylphosphate or on a polyurethane polyether foam (PUF).

For example, the at least one rare earth element can be substantiallyselectively removed by means of a liquid-liquid extraction. For example,the liquid-liquid extraction can be carried out by using an extractingagent.

For example, the process can comprise selectively precipitating at leasttwo members chosen from the at least one rare earth element that is inthe form of ions, the second metal ion and the first metal ion. Forexample, each of the members can be precipitated separately or together.

According to another example, the processes can comprise:

leaching the at least one material with HCl so as to obtain the leachatecomprising a first metal ion a second metal ion and the at least onerare earth element, and the solid and separating the leachate from thesolid;

substantially selectively removing the second metal ion from theleachate, thereby obtaining a composition comprising the first metalion, and the at least one rare earth element; and

substantially selectively at least partially removing the first metalion from the composition, thereby obtaining a liquor comprising the atleast one rare earth element.

According to another example, the processes can comprise:

leaching the at least one material with HCl so as to obtain the leachatecomprising a first metal ion, a second metal ion, and the at least onerare earth element, and the solid and separating the leachate from thesolid;

substantially selectively removing the second metal ion from theleachate, thereby obtaining a composition comprising the first metalion, and the at least one rare earth element; and

substantially selectively at least partially removing the first metalion from the composition, thereby obtaining a liquor comprising the atleast one rare earth element.

According to another example, the leaching can be carried out at a pH ofabout 0.5 to about 2.5, then the second metal ion can be precipitated ata pH of at least about 9.5, then the first metal ion can be precipitatedat a pH of about 8 to about 9, and then at least one scandium ion can beprecipitated at a pH of about 7 to about 8.

According to another example, the leaching can be carried out at a pH ofabout 0.5 to about 1.5, then the second metal ion can be precipitated ata pH of at least about 10.5, then the first metal ion can beprecipitated at a pH of about 8 to about 9, and then at least onescandium ion can be precipitated at a pH of about 7 to about 8.

According to another example, the leaching can be carried out at a pH ofabout 0.5 to about 1.5, then the second metal ion can be precipitated ata pH of at least about 11, then the first metal ion can be precipitatedat a pH of about 8 to about 9, and then at least one scandium ion can beprecipitated at a pH of about 7 to about 8.

For example, scandium can be precipitated from a by-product generatedduring the process.

For example, scandium can be precipitated from a solution generatedduring the process. For example, scandium can be precipitated usingHNO₃.

For example, the at least one rare earth element can be substantiallyselectively precipitated, extracted and/or isolated by at least onetechnique chosen from ion exchange resin, extraction by means ofsolvent(s) and adsorption.

For example, the at least one rare earth element can be substantiallyselectively precipitated, extracted and/or isolated by means of an ionexchange resin.

For example, the at least one rare earth element can be substantiallyselectively precipitated, extracted and/or isolated by means of aliquid-liquid extraction.

For example, the at least one rare earth element can be substantiallyselectively precipitated, extracted and/or isolated by means of anelectrowinning process.

According to another example, the leaching can be carried out at a pH ofabout 0.5 to about 2.5, then the second metal ion can be precipitated ata pH of at least about 9.5, then the first metal ion can be precipitatedat a pH of about 8 to about 9, and then and then the at least one rareearth element can be substantially selectively extracted.

According to another example, the leaching can be carried out at a pH ofabout 0.5 to about 1.5, then the second metal ion can be precipitated ata pH of at least about 10.5, then the first metal ion can beprecipitated at a pH of about 8 to about 9, and then the at least onerare earth element can be substantially selectively extracted.

According to another example, the leaching can be carried out at a pH ofabout 0.5 to about 1.5, then the second metal ion can be precipitated ata pH of at least about 11, then the first metal ion can be precipitatedat a pH of about 8 to about 9, and then the at least one rare earthelement can be substantially selectively extracted.

For example, the at least one material/acid ratio can be about 1/10 inweight by volume.

According to another example, the processes can further comprise atleast one of

-   -   at least partially removing the second metal ion from the        leachate by substantially complexing the second metal ion with        an extracting agent;    -   selectively precipitating the second metal ion;    -   selectively precipitating the first metal ion; and    -   at least partially removing the first metal ion from the        leachate by substantially complexing the first metal ion with        another extracting agent.

According to another example, the processes comprise:

-   -   leaching the at least one material with HCl so as to obtain a        leachate comprising a first metal ion and a second metal ion and        a solid residue, and separating the leachate from the solid        residue;    -   at least partially removing the second metal ion from the        leachate by substantially selectively precipitating the second        metal ion by reacting the leachate with a base so as to obtain        an aqueous composition rich in the first metal ion and        comprising the at least one rare element and a precipitate, and        removing the precipitate from the composition;    -   purifying the aqueous composition by substantially selectively        precipitating the first metal ion, thereby obtaining another        composition comprising the at least one rare element and another        precipitate, removing the precipitate from the composition; and    -   substantially selectively extracting the at least one rare        element from the another composition.

According to another example, the processes can comprise:

-   -   leaching the at least one material with HCl so as to obtain a        leachate comprising a first metal ion and a second metal ion and        a solid residue, and separating the leachate from the solid        residue,    -   at least partially removing the second metal ion from the        leachate by substantially selectively precipitating the second        metal ion by reacting the leachate with a base so as to obtain        an aqueous composition rich in the first metal ion and        comprising the at least one rare element and a precipitate, and        removing the precipitate from the composition;    -   substantially selectively extracting the first metal ion from        the aqueous composition by means of a hollow fiber membrane, or        by a liquid-liquid extraction, and removing the extracted first        metal ion, thereby obtaining an aqueous composition depleted in        the first metal ion comprising the at least one rare element;        and    -   substantially selectively extracting the at least one rare        element from the aqueous composition.

According to another example, the processes can comprise:

-   -   leaching the at least one material with HCl so as to obtain a        leachate comprising a first metal ion and a second metal ion and        a solid residue, and separating the leachate from the solid        residue;    -   at least partially removing the second metal ion from the        leachate by substantially selectively complexing the second        metal ion with an extracting agent so as to obtain an aqueous        composition rich in the first metal ion comprising the at least        one rare earth element;    -   purifying the aqueous composition by substantially selectively        precipitating the first metal ion, thereby obtaining another        composition comprising the at least one rare element and another        precipitate, removing the precipitate from the composition; and    -   substantially selectively extracting the at least one rare        element from the another composition.

According to another example, the processes can comprise:

-   -   leaching the at least one material with HCl so as to obtain a        leachate comprising a first metal ion and a second metal ion and        a solid residue, and separating the leachate from the solid        residue;    -   at least partially removing the second metal ion from the        leachate by substantially selectively complexing the second        metal ion with an extracting agent so as to obtain an aqueous        composition rich in the first metal ion comprising the at least        one rare earth element;    -   substantially selectively extracting the first metal ion from        the aqueous composition by means of a hollow fiber membrane, or        by a liquid-liquid extraction, and removing the extracted first        metal ion, thereby obtaining an aqueous composition depleted in        the first metal ion comprising the at least one rare element;        and    -   substantially selectively extracting the at least one rare        element from the aqueous composition depleted in the first metal        ion.

According to another example, the processes can comprise:

-   -   leaching the at least one material with HCl so as to obtain a        leachate comprising a first metal ion and a second metal ion and        a solid residue, and separating the leachate from the solid        residue;    -   at least partially removing the first metal ion from the        leachate by substantially selectively precipitating the first        metal ion so as to obtain an aqueous composition rich in the        second metal ion comprising the at least one rare element and a        precipitate, and removing the precipitate from the composition;    -   substantially selectively precipitating the second metal ion        from the aqueous composition rich in the second metal ion, and        removing the precipitate therefrom, thereby obtaining thereby        obtaining an aqueous composition depleted in the second metal        ion and comprising the at least one rare element; and    -   substantially selectively extracting the at least one rare        element from the aqueous composition depleted in the second        metal ion.

For example, the first metal ion can comprises at least one aluminumion.

For example, the second metal ion can comprise at least one iron ion.

For example, the at least one aluminum ion can be precipitated under theform of AlCl₃ in a crystallizer, for example, by sparging gaseous HCl.

For example, the at least one iron ion can be precipitated under theform of Fe₂O₃ by means, for example, of an hydrolysis.

For example, the aqueous composition rich in the first metal ion can bepurified by complexing the first metal ion with an extracting agent soas to obtain a complex, separating the complex form the composition andprecipitating the first metal ion.

For example, the aqueous composition rich in the first metal ion can bepurified by complexing impurities contained in aqueous composition richin the first metal ion with an extracting agent, at least partiallyremoving the complexed impurities from the composition and precipitatingthe first metal ion.

According to another example the processes can comprise:

-   -   1—leaching argillite with at least one acid (for example a        solution of HCl or gaseous HCl (for example at pH of about 0.5        to about 1.5 or about 0.8 to about 1.2). The leaching cal also        be carried out under pressure;    -   2—removing iron by ionic precipitation by raising th at pH of        about 10 to about 12 or about 11 to about 12 (or extracting it        with extracting agents) and filtering out all non-soluble        hydroxides;    -   3—precipitating aluminum at a pH of about 7.5 to about 9.0 or        about 7.8 to about 8.2 and filtering aluminium hydroxide as a        solid;    -   4—optionally purifying aluminum (Al(OH)₃) using at least one of        a liquid-liquid extraction, a membrane and an extracting agent        suitable for complexing aluminum ions; and    -   5—precipitating, extracting and/or isolating at least one rare        earth element can be carried out after at least one of steps 1,        2, 3 and 4.

For more details and explanations regarding at least certain portions ofsteps 1 to 4, WO2008141423, which is hereby incorporated by reference inits entirety, can be referred to.

According to another example the processes can comprise:

-   -   1—leaching argillite with an acid (for example a solution of HCl        18-32 wt %. The leaching can also be carried out under pressure        such as about 350 KPag to about 500 KPag during about 4 to about        7 hours;    -   2—removing iron by ionic precipitation by raising the at pH of        about 10 to about 12 or about 11 to about 12 (or extracting it        with extracting agents) and filtering out all non-soluble        hydroxides;    -   3—precipitating aluminum at a pH of about 7.5 to about 9.0 or        about 7.8 to about 8.2 and filtering aluminium hydroxide as a        solid;    -   4—optionally purifying aluminum (Al(OH)₃) using at least one of        a liquid-liquid extraction, a membrane and an extracting agent        suitable for complexing aluminum ions; and    -   5—precipitating, extracting and/or isolating at least one rare        earth element can be carried out after at least one of steps 1,        2, 3 and 4.

According to another example as shown in FIG. 1, the processes caninvolve the following steps (the reference numbers in FIG. 1 correspondto the following steps):

1—The aluminum-bearing material is reduced to an average particle sizeof about 50 to about 80 μm.

2—The reduced and classified material is treated with hydrochloric acidwhich allows for dissolving, under a predetermined temperature andpressure, the aluminum with other elements like iron, magnesium andother metals including rare earth. The silica remains totallyundissolved.

3—The mother liquor from the leaching step then undergoes a separation,a cleaning stage in order to separate the purified silica from the metalchloride in solution.

4—The spent acid (leachate) obtained from step 1 is then brought up inconcentration with dry and highly concentrated gaseous hydrogen chlorideby sparging this one into a crystallizer. This results into thecrystallization of aluminum chloride hexahydrate (precipitate) with aminimum of other impurities. Depending on the concentration of ironchloride at this stage, further crystallization step(s) can be required.The precipitate is then separated from the liquid.

5—The aluminum chloride hexahydrate is then calcined (for example bymeans of a rotary kiln, fluid bed, etc) at high temperature in order toobtain the desired alumina. Highly concentrated gaseous hydrogenchloride is then recovered and excess is brought in aqueous form to thehighest concentration possible so as to be used (recycled) in the acidleaching step.

6—Iron chloride (the liquid obtained from step 4) is thenpre-concentrated and hydrolyzed at low temperature in view of the Fe₂O₃(hematite form) extraction and acid recovery from its hydrolysis. Allheat recovery from the calcination step (step 5), the leaching partexothermic reaction (step 1) and other section of the process is beingrecovered into the pre-concentrator.

10—After the removal of hematite, a solution rich in rare earth elementscan be processed by using any one of the processes described in thepresent disclosure for recovering rare earth elements fromaluminum-bearing materials. For example, the recovered rare earthelements can be in various forms such oxides, chlorides, hydroxides etc.As previously indicated in the present disclosure, the expression “rareearth element” can also encompass “rare metal” and thus, in step 10,rare metals can also be recovered. For example, rare metals can be underthe form of rare metals oxides. Thus, in FIGS. 1 and 2, the step 10 canbe, for example, the processes shown in FIG. 3 or in FIGS. 4a and 4 b.

Other non-hydrolyzable metal chlorides (Me-Cl) such as MgCl₂ and othersthen undergo the following steps:

7—The solution rich in magnesium chloride and other non-hydrolyzableproducts at low temperature is then brought up in concentration with dryand highly concentrated gaseous hydrogen chloride by sparging it into acrystallizer. This results into the precipitation of magnesium chlorideas an hexahydrate.

8—Magnesium chloride hexahydrate is then calcined (either through arotary kiln, fluid bed, etc.) and hydrochloric acid at very highconcentration is thus regenerated and brought back to the leaching step.

9—Other Me-Cl undergo a standard pyrohydrolysis step where mixed oxidescan be produced and hydrochloric acid at the azeotropic point (20.2%wt.) is regenerated.

For example, the liquid can be concentrated to a concentrated liquidhaving an iron chloride concentration of at least 30% by weight; andthen the iron chloride can be hydrolyzed at a temperature of about 155to about 350° C. while maintaining a ferric chloride concentration at alevel of at least 65% by weight, to generate a composition comprising aliquid and precipitated hematite, and recovering the hematite.

For example, the liquid can be concentrated to a concentrated liquidhaving an iron chloride concentration of at least 30% by weight; andthen the iron chloride can be hydrolyzed at a temperature of about 155to about 350° C. while maintaining a ferric chloride concentration at alevel of at least 65% by weight, to generate a composition comprising aliquid and precipitated hematite; recovering the hematite; andrecovering rare earths from the liquid. For example, the process canfurther comprise, after recovery of the rare earths, reacting the liquidwith HCl so as to cause precipitation of MgCl₂, and recovering same.

As previously indicated, various aluminum-bearing materials can be usedas starting material of the processes disclosed in the presentdisclosure. Examples with clays and bauxite have been carried out.However, the person skilled in the art will understand that thecontinuous processes can handle high percentages of silica (>55%) andimpurities as well as relatively low percentages of aluminum (forexample as low as about 15%) and still being economically andtechnically viable. Satisfactory yields can be obtained (>93-95%) onAl₂O₃ and greater than 75% on rare earth elements. No pre-thermaltreatment in most cases are required. The processes disclosed in thepresent disclosure involve special techniques on leaching and acidrecovery at very high strength, thereby offering several advantages overalkaline processes.

In step 1 the mineral, whether or not thermally treated is crushed,milled, dried and classified to have an average particle size of about50 to about 80 μm.

In step 2, the milled raw material is introduced into the reactor andwill undergo the leaching phase.

The leaching hydrochloric acid used in step 2 is a recycled orregenerated acid from steps 5, 6, 8 and 9 and its concentration can varyfrom 15% to 45% weight. percent. Higher concentration can be obtainedusing a membrane separation, a cryogenic and/or high pressure approach.The acid leaching can be carried out under pressure and at temperatureclose to its boiling point thus, allowing a minimal digestion time andextended reaction extent (90%-100%). Leaching (step 2) can beaccomplished in a semi-continuous mode where spent acid with residualfree hydrochloric acid is replaced by highly concentrated acid at acertain stage of the reaction or allowing a reduced acid/mineral ratio,thereby reducing reaction time and improving reaction kinetics. Forexample, kinetic constant k can be: 0.5-0.75 g/mole·L

As previously indicated, alkali metals, iron, magnesium, calcium,potassium, rare earth elements and other elements will also be in achloride form at different stages. Silica will remain undissolved andwill undergo (step 3) a liquid/solid separation and cleaning stage. Theprocesses of the present disclosure tend to recover maximum amount offree hydrochloric acid left and chlorides in solution in order tomaximize hydrochloric acid recovery yield, using techniques such as rakeclassifying, filtration with band filters, centrifugation, and others.Mother liquor free of silica is then named as spent acid (various metalchlorides and water) and goes to the crystallization step (step 4).

In step 4, the spent acid (or leachate) with a substantial amount ofaluminum chloride is then saturated with dry and highly concentratedgaseous hydrogen chloride obtained or recycled from step 5, whichresults in the precipitate of aluminum chloride hexahydrate(AlCl₃.6H₂O). The precipitate retained is then washed and filtered orcentrifuged before being fed to the calcination stage (step 5). Theremaining of the spent acid from step 4 is then processed to acidrecovery system (steps 6 to 8) where pure secondary products will beobtained.

In step 5, aluminum oxide (alumina) is directly obtained from hightemperature conditions. The highly concentrated hydrogen chloride ingaseous form obtained can be fed to steps 4 and 7 for crystallization.The excess hydrogen chloride is absorbed and used as regenerated acid tothe leaching step 2 as highly concentrated acid, higher than theconcentration at the azeotropic point (>20.2%). For example, such aconcentration can be about 25 to about 45 weight % or between 25 and 36weight %.

After step 4, various chlorides derivatives of (mainly iron chlorides,magnesium chloride and rare earth element in the form of chlorides) arenext subjected to an iron extraction step. Such a step can be carriedout for example by using the technology disclosed in WO 2009/153321,which is hereby incorporated by reference in its entirety.

In step 6, a hydrolysis at low temperature (155-350° C.) is carried outand pure Fe₂O₃ (hematite) is being produced and hydrochloric acid of atleast 15% concentration is being regenerated. The method as described inWO 2009/153321 is processing the solution of ferrous chloride and ferricchloride, possible mixtures thereof, and free hydrochloric acid througha series of steps pre-concentration step, oxidation step where ferrouschloride is oxidized into ferric form, and finally through an hydrolysisstep into an operational unit called hydrolyser where the ferricchloride concentration is maintained at 65 weight % to generate a richgas stream where concentration ensures a hydrogen chloride concentrationof 15-20.2% and a pure hematite that will undergo a physical separationstep. Latent heat of condensation is recovered to the pre-concentrationand used as the heating input with excess heat from the calcinationstage (step 5).

The mother liquor left from the hydrolyser (step 6), after iron removal,is rich in other non-hydrolysable elements and mainly comprisesmagnesium chloride or possible mixture of other elements (variouschlorides) and rare earth elements.

Rare earth elements in form of chlorides are highly concentrated inpercentage into the hydrolyser operational unit (step 6) and areextracted from the mother liquor (step 10) where the processes definedin the present disclosure for recovering rare earth elements fromaluminum-bearing materials can be employed. For example, rare earthelements under various forms can thus be extracted. For example, it canbe under the form of oxides. REO. The processes of the presentdisclosure for recovering rare earth elements can allow, for example, toconcentrate to a high concentration the following rare earth elements,within the hydrolyser: scandium (Sc), galium (Ga), yttrium (Y),dysperosium (Dy), cerium (Ce), praseodynium (Pr), neodynium (Nd),europium (Eu), samarium (Sm), gadolinium (Gd), lanthanum (La), erbium(Er). Of course, the at least one rare earth element that will berecovered will depend upon the nature of the startin material(aluminum-bearing material).

The spent acid liquor from steps 6 and 10 rich in value added metals,mainly magnesium, is processed to step 7. The solution is saturated withdry and highly concentrated gaseous hydrogen chloride from step 5, whichresults in the precipitation of magnesium chloride hexahydrate. Theprecipitate retained, is fed to a calcination stage step 8 where pureMgO (>98% wt.) is obtained and highly concentrated hydrochloric acid(for example of at least 38%) is regenerated and diverted to theleaching step (step 2). An alternative route for step 7 is using drygaseous hydrochloric acid from step 8.

In step 9, metal chlorides unconverted are processed to a pyrohydrolysisstep (700-900° C.) to generate mixed oxides and where hydrochloric acidfrom 15-20.2% wt. concentration can be recovered.

According to another example as shown in FIG. 2, the processes can besimilar to the example shown in FIG. 1 but can comprise some variants asbelow discussed.

In fact, as shown in FIG. 2, the process can comprise (after step 6 orjust before step 10) an internal recirculation back to thecrystallization step 4. In such a case, The mother liquor from thehydrolyser (step 6) can be recirculated fully or partially to thecrystallization of step 4 where a concentration increase will occur withrespect to the non-hydrolyzable elements including rare earth elements.

Such a step can be useful for significantly increasing the concentrationof rare earth elements, thereby facilitating their extraction in step10.

With respect to step 7, the solution rich in magnesium chloride andother non-hydrolyzable products at low temperature is, as previouslydiscussed, then brought up in concentration with dry and highlyconcentrated gaseous hydrogen chloride by sparging it into acrystallizer. This can result into the precipitation of magnesiumchloride as an hexahydrate (for example after sodium and potassiumchloride removal).

As shown in FIG. 2, an extra step 11 can be added. Sodium chloride canundergo a chemical reaction with sulfuric acid so as to obtain sodiumsulfate and regenerate hydrochloric acid at the azeotropic point.Potassium chloride can undergo a chemical reaction with sulfuric acid soas to obtain potassium sulfate and regenerate hydrochloric acid at theazeotropic point.

Certain prophetical examples are hereby provided in the presentdisclosure for substantially selectively recovering, precipitating,extracting and/or isolating at least one rare earth element. This can bedone, for example from the leachate and/or the precipitate and any otherdownstream derivatives, solutions, precipitates, compositions orliquors.

For example, recovering, precipitating, extracting and/or isolating atleast one rare earth element can be carried out by:

-   -   precipitating least one rare earth element (for example at a pH        of about 6 to about 8, 7 to about 8, or 7 to about 7.5);    -   using an ion exchange resin (for example, as described in U.S.        Pat. No. 4,816,233 (hereby incorporated by reference in its        entirety)); extraction by means of solvent(s) (for example a        liquid-liquid extraction can be carried out using        di-(2-ethylhexyl) phosphoric acid (HDEHP (also called DEHPA or        D2EHPA)), mono(2-ethylhexyl)2-ethylhexyl phosphonate (HEH/EHP),        octyl phenyl phosphate (OPAP), 2-ethylhexylphosphonic acid        mono-2-ethylhexyl ester (PC88A) and optionally toluene (for        example as described in Kao et al. in Chemical Engineering        Journal, Volume 119, Issues 2-3, Jun. 15, 2006, pages 167-174        (hereby incorporated by reference in its entirety)) or by means        of extracted using an alkyl phosphate (for example as described        in U.S. Pat. No. 3,013,859 (hereby incorporated by reference in        its entirety));    -   using an extracting agent (for example using        bis(2,4,4-trimethylpentyl)monothiophosphinic acid or a        derivative thereof);    -   adsorption on activated charcoal (activated carbon adsorption)        optionally modified with tributyl phosphate or on a polyurethane        polyether foam (PUF); (for example as described in Zhou et al.        in RARE METALS, Vol. 27, No. 3, 2008, p 223-227 (hereby        incorporated by reference in its entirety))    -   extraction with hollow fiber membranes; and    -   using an electrowinning technology (for example as described in        US 2004/0042945 (hereby incorporated by reference in its        entirety)).

For example, scandium can be precipitated (optionally using HNO₃) from aresidual solution generated during the process (for example when iron isprecipitated and/or when aluminum is precipitated).

For example, when substantially selectively precipitating, extractingand/or isolating at least one rare earth element from the leachateand/or the precipitate and any other downstream derivatives, varioussequences can be carried out i.e. depending on the nature of thestarting material and the rare earth elements present, a given rareearth element can be more easily extracted before or after another givenrare earth element.

For example, as shown in FIG. 3, in a mixture or liquor comprising HCl,water and rare elements in the form of chlorides, the mixture can betreated with an extracting agent in order to extract GaCl₃ therefrom,thereby obtaining a Ga-free solution. Such an extracting agent can be,for example, octyl phenyl phosphate (OPAP) or 2-ethylhexylphosphonicacid mono-2-ethylhexyl ester (PC88A) and toluene. GaCl₃ can then beprecipitated and then converted into Ga₂O₃ by heating it.

Then, the Ga-free solution can be treated with an extracting agent (forexample SME 529™, tri-butyl phosphate or di-isoamylmethyl phosphonate,di-(2-ethylhexyl) phosphoric acid,7-(4-ethyl-1-methyloctyl)-8-hydroxyquinoline (Kelex 100™) in n-heptanewith the addition of 10% n-decanol.) for substantially selectivelyextracting cerium chloride therefrom so as to obtain a Ce-free solution.CeCl₃ can be eventually converted into CeO₂.

Then, the Ce-free solution can be treated with an extracting agent suchas di-(2-ethylhexyl) phosphoric acid or di-(2-ethylhexyl) phosphinicacid so as substantially selectively extract Sc and to provide a Sc-freesolution. The extracted Sc can be treated with an oxidizer (such asNaOH) so as to provide Sc₂O₃.

Then, the various remaining rare earth elements (Pr, Nd, Sm, Eu, La, Gd,Y, Dy, Er etc.) in the Sc-free solution can be extracted in differentpossible orders.

For example, it has to be noted that the process schematized in FIG. 3can be used as a component of various other processes such as theprocess schematized in FIG. 1 or in FIG. 2. For example, the step 10 ofFIGS. 1 and 2 can be the process schematized in FIG. 3.

For example, as shown in FIGS. 4a and 4b , a process for extracting rareearth elements can comprise:

-   -   Ferric reduction to ferrous using iron;    -   Separation of gallium from the ferrous chloride solution;    -   Precipitation and pre-concentration of rare earth elements from        the raffinate;    -   Re-leaching and fractioning of the rare earth elements into        light (LRE) and heavy (HRE) groups;    -   Separation of yttrium from scandium and heavy rare earth        elements; and    -   Separation of scandium and heavy rare earth elements

The reduction of ferric to ferrous with a reducing agent (such asmetallic iron) can be used so as to prevent iron coextraction or ironprecipitation. The reaction time can be very short and it can generateheat.

As shown in FIGS. 4a and 4b , The ferric chloride feed solution 101 canbe fed to an agitated reaction tank and a reducing agent (for examplemetallic iron 102) can added so as to allow for converting ferricchloride to ferrous chloride (see “Ferric Removal”). After asolid-liquid separation (s/I separation), the resulting filtrate 103 canbe further treated in a gallium extraction circuit. A filter cake,containing solid material and iron, can be dewatered and the resultingslurry can then be prepared for disposal.

Gallium can then be extracted with an organic solution containing anextracting agent (for example tri-butyl phosphate (TBP) dissolved inkerosene) (see “Gallium Recovery”). The rare earth and iron can thus beleft in the raffinate. The extraction can vary as a function of thechloride ion concentration. For example, the higher chloride ionconcentration, the stronger tendency for gallium complex formation andthe better extraction.

For example, for gallium (recovery from hydrochloric acid solutions,reagents such as tri-butyl phosphate or tertiary amines (e.g. Alamine336) can be used. For example, when increasing hydrochloric acid (HCl)concentration, gallium extraction can rise to a maximum and can thendecrease again. For example, HCl concentration can be increased up toabout 4 M HCl for the gallium extraction. Under these conditions,gallium can be present in the form of HGaCl₄ complex and TBP extractedgallium as a trisolvate (HGaCl₄*3TBP) (for example when the extractingagent is TBP).

Co-extracted iron, accumulated in the organic phase can be scrubbed withhydrochloric acid (see “Gallium Strip Liquor”). The resulting organicsolution, containing gallium can be fed to a stripping circuit wheregallium is stripped with water 104. The raffinate 106, containingferrous chloride and the rare earth elements, can then be fed to therare earth precipitation section (see “Bulk REE Removal”). The finalstrip liquor 105 contains gallium.

For example, oxalate precipitation of rare earth elements result in verylow solubility of the compounds in aqueous solution. The precipitationof rare earth oxalates can be achieved by addition of a precipitationreagent 107. For example, oxalic acid 107 can be used for theprecipitation. For example, precipitating agent that are effective forprecipitating rare earth elements of the trivalent (such as oxalate(from oxalic acid)) can be used. For example, such precipitating agentscan have provide a very low solubility in aqueous solution to so-formedprecipitate.

An overflow from the primary rare earth elements precipitation 109 canbe fed to a ferrous treatment circuit. After filtration, the filtercake, containing the rare earth elements, can be fed to a washing anddewatering unit. A resulting slurry 108 can then be prepared forre-leaching (see “REE-Re-leaching”). Re-leaching of the rare earthfilter cake can be carried out using hydrochloric acid 110.

From a pre-concentrated and pH adjusted chloride solution 111, thatcontains for example about 150 to about 250 g/L, rare earth elementsyttrium, scandium and the heavy rare earth (HRE) are extracted (see“Primary REE Recovery”) with an extracting agent (for example(di-(2-ethylhexyl)phosphoric acid (D2EHPA) or 2-ethylhexylphosphonicacid mono-2-ethylhexyl ester (PC88A (also called Lonquest™ 801) inkerosene)). Scandium, the other HRE and also yttrium can be extractedand leaving the light rare earth elements (LRE) in a raffinate 113.

A loaded organic phase can then be selectively scrubbed withhydrochloric acid (2 M HCl) to remove the co-extracted LRE. A secondaryscrubbing section can remove europium by using weak hydrochloric acid (1to 1.5 M HCl). The extract, containing yttrium, scandium and the HRE,can then be stripped with strong acid (3.5 M HCl) 112.

The HRE strip liquor 114, containing yttrium and scandium, can betreated further to obtain more than 90% Y₂O₃ and Sc₂O₃ in a firstcircuit of a double solvent extraction purification process. In a firststep, the aqueous solution, containing about 25 g/L (of rare earthelements in the form of oxides) and 0.4 M HCl, can be brought intocontact with an extracting agent (for example(di-(2-ethylhexyl)phosphoric acid (D2EHPA) or 2-ethylhexylphosphonicacid mono-2-ethylhexyl ester (PC88A (also called Lonquest™ 801) inkerosene)) (see “Secondary REE Recovery”). The loaded organic phase isthen scrubbed with diluted hydrochloric acid. Scandium, yttrium and HREcan be extracted by the reagent and finally stripped with stronghydrochloric acid 115 at a high oxide/acid ratio. The final strip liquorwould have a concentration in rare earth elements oxides of about 40 g/Land about 1 M HCl. This solution is partially neutralized.

This pre-treated strip liquor 116 can be further extracted with anextracting agent (for example tri-butyl phosphate (TBP) in kerosene).The treatment can be done in a multi stage procedure, and ending up in afinal stripping of the loaded organic with water 117. All HRE andscandium can thus extracted, leaving yttrium in a raffinate 119. A finalstrip liquor 118, containing HRE, forms the source for furtherseparation of scandium and heavy rare earth. In order to do so, variouspossible extracting agents can be used such as di-(2-ethylhexyl)phosphoric acid.

The separation of scandium from other HRE, (for example dysprosium anderbium) can be carried out using a further solvent extractionpurification circuit, similar to the yttrium separation and purificationprocess and previously described. Thus, the extracting agent can be thesame or a different one, the strip solution 120 can be the same than117, thereby providing a scandium raffinate 121 and a strip liquor 122comprising europium and erbium.

As an alternative, yttrium can be extracted as described in U.S. Pat.No. 3,751,553 (hereby incorporated by reference in its entirety). Infact, yttrium can be extracted starting from a xenotime concentrate. Itcan be done by using three solvent extraction circuits. In a first step,DEHPA can be used to separate yttrium. In a second step, tri(caprylmethyl) ammonium nitrate (Aliquat 336) can be used to extract andseparate cerium and leave yttrium in the raffinate. In a third step, Tm,Yb, and Lu can be extracted by means of tri (caprylmethyl) ammonium thiocyanate. In this extraction loop, yttrium behaves like a cerium element.From this step, high-purity of yttrium oxide can be obtained.

According to another alternative, yttrium oxide can be extracted in twosteps i.e. tri (caprylmethyl) ammonium nitrate can be used to separate amixture La—Er/Y—Lu and then, a purification of yttrium is carried outusing versatic acid.

Solvent extraction is a selective separation procedure for isolating andconcentrating valuable elements from an aqueous solution with the aid ofan organic solution. In the procedure the aqueous solution containingthe element of interest, often at a low concentration and together withother dissolved substances (pollutants), is mixed (extraction) with anorganic solvent containing a reagent. The element of interest reactswith the reagent to form a chemical compound that is more soluble in theorganic than in the aqueous solution. As a consequence, the element ofinterest is transferred to the organic solution.

Subsequently, in order to recover the extracted substance, the organicsolution is mixed (stripping) with an aqueous solution whose compositionis such that the chemical compound between the element and the reagentis split and, thus, the element is recovered in the “new” aqueoussolution, in a pure form. The concentration of the element in the “new”aqueous solution may be increased, often to 10-100 times that of theoriginal aqueous solution, through adjustment of the liquid flow rates.Freed from the extracted element, the organic solution is returned forfurther extraction, either directly or after a fraction of it has beencleansed of impurities.

Important factors that govern this solvent extraction process can be,for example, the number of extraction, scrubbing and stripping stages,organic solvent concentration and diluent.

In a typical solvent extraction process, the aqueous phase, containingthe rare earth elements, can be for example a chloric or nitric acidicsolution. The organic phase comprises an extracting agent as thoserecited in the present disclosure or alternatives in an organic solventsuch as an aliphatic diluent.

Solvent extraction technique can be used as separation and purificationprocedure for the rare earth elements. Some of the following propertiesare particularly relevant when selecting an extracting agent or chemicalextractant:

High selectivity over other unwanted metals and acids during theextraction process,

High transfer capacity on the extractant,

Good chemical stability,

Fast kinetics.

For example, precipitation denotes the removal of the rare earthelements from solution by the addition of a chemical reagent to form anew, less soluble (solid) compound. For example, a completeprecipitation can be carried out by oxalate, hydroxide, or othercompounds.

Hydroxide precipitation and double sulphate can also be used. For largescale operation, ammonia can be used for carrying out hydroxideprecipitation from nitrate or chloride solutions. The double sulphatesRE₂(SO₄)₃*Na₂SO₄*nH₂O can be precipitated by either addition of sodiumsulphate to the solution containing rare earth elements. Theprecipitation reaction of trivalent rare earth elements in aqueoussolution is according to the following equation:REE³⁺+3H₂O→REE(OH)₃+3H⁺

The below presented examples are non-limitative and are used to betterexemplify the processes of the present disclosure.

Example 1 Preparation of an Aluminum-Bearing Material Sample

The aluminum-bearing material (for example argillite) can be finelycrushed in order to help along during the following steps. For example,micronization can shorten the reaction time by few hours (about 2 to 3hours). In order to remove most of the iron, a leaching step at roomtemperature is optionally carried out between the crushing step and thecalcination step. This operation is, for example, carried out withhydrochloric acid HCl (12 M or 32 wt %) and an argillite/acid ratio(weight/volume) of 1:5 is used. Depending on experimental conditions(sizes of the particles, time of treatment, agitation system), about 65%to about 93% of the iron can then be dissolved. However, this leachingstep can also bring in a certain percentage of the aluminum (0-5%). Thelast step of the preparation of argillite comprises calcining thepretreated argillite. This can be accomplished at a calcinatingtemperature greater than 550° C. for a period of about 1 to 2 hours. Forexample, a heat treatment makes it possible to increase the quantity ofextracted aluminum by about 30% to about 40% for the same period oftime. In others words, the quantity of extracted aluminum is doubled.When leaching at room temperature is carried out, a phase separationbefore calcination can be made in order to recover the acid and reduceheating costs.

Acid Leaching

Acid leaching can comprise reacting the crushed and roasted argillitewith at least one acid solution (for example HCl) at elevatedtemperature during a given period of time. For example, theargillite/acid ratio can be of about of 1:10 (weight/volume), the HClconcentration can be of about 6 M or about 18 to 20 wt %, thetemperature can be of about 100° C. to about 110° C., and the reactiontime can be of about 30 minutes to about 7 hours. Under such conditions,more than about 90% of the aluminum and about 100% of the iron can beextracted in addition to impurities. Alternatively, the leaching can becarried out at a temperature of about 150° C. to about 175° C. at apressure of about 350 KPag to about 500 KPag during about 4 to about 7hours.

During the second half of such a treatment (for example the last 2 or 3hours), a portion of the excess acid can be recovered by flashing andcondensation. Once the extraction is terminated, the solid (argilliteimpoverished in metals) can be separated from the liquid by decantationor by filtration, after which it is washed. The residual leachate andthe washing water may be completely evaporated. The correspondingresidue can thereafter be counter currently washed many times with waterso as to decrease acidity and to lower the quantities of base used (forexample, NaOH, KOH, Ca(OH)₂, Mg(OH)₂, etc.) that are required to adjustthe pH during iron removal. The acid recovered will can be re-utilizedafter having adjusted its titer either by adding either gaseous HCl, orby adding concentrated HCl (12 M). After the reaction, the titer of theacid can vary from about 4 M to about 6 M depending on experimentalconditions. With respect to the solid, it represents about 65% to about75% of the initial mass of argillite, it can be valorized and be usedagain either as an ion exchange resin, or as an adsorbent.

Alternatively, the HCl leaching can be carried out under pressure (so toincrease the reaction temperature) into an autoclave.

The rare earth element(s) recovery can be made, for example, at thisstage, after carrying out the above mentioned acid leaching.

Removal of Iron

Several alternatives are proposed in the present disclosure for carryingout iron removal. For example, iron removal can be carried out bysubstantially selectively precipitating iron ions at certain pH values.Alternatively, some extracting agents can be used as described inWO2008141423. A membrane can also be used in combination with suchextracting agents

For example, removal of iron can be carried out by ionic precipitationof the latter in basic medium for example at a pH of at least 10 or at apH of about 11.5 to about 12.5. The pH can also be about 3 to about 6,or about 3 to about 5 or about 3 to about 4. Such a step can be made byadding a solution of NaOH, for example at a concentration of 10 M. Otherbases such as KOH can also be used. Then, all that is required is toseparate the solid portion from the liquid portion by filtration,decantation or centrifugation and to rinse the solid by means of adiluted base, such as a solution of NaOH (for example NaOH at aconcentration of 0.01 M to 0.02 M). Then, the solid is washed contercurrently with water. The liquid portion comprises aluminum andalkaline-earths A substantially complete removal of the iron and ofnearly all the impurities (other metals) can thus be achieved asinsoluble and washed hydroxides. Optionally, it is possible to recoveriron by using a refining step by liquid-liquid extraction through ahollow fiber membrane.

Alternatively, removal of iron can be carried out by using an extractingagent and a hollow fiber membrane. Various extracting agents that couldsubstantially selectively complex iron ions over aluminum ions (oraluminum ions over iron ions) could be used in such a step depending anAl/Fe ratio. For example, extraction can be carried out by using HDEHP(or DEHPA) di(2-ethylhexyl)phosphoric acid) as an extracting agentadapted to complex iron ions. A concentration of about 1 M of HDEHP canbe used in an organic solvent, such as heptane or any hydrocarbonsolvent. Such an extraction can require relatively short contact times(few minutes). For example, the pH of the order of 2 can be used andaqueous phase/organic phase ratio can be of about 1:1. It was observedthat is possible to extract from 86% to 98% iron under such conditions.It will be understood that in the present case, iron is trapped in theorganic phase. To recover iron in an aqueous phase, a reverse extractionwith hydrochloric acid (2 M or 6 M) and organic phase/acidic phase ratioof about 1:0.5 can then be carried out. In such a case, the resultingaqueous phase is rich in Fe³⁺ ions.

The rare earth element(s) recovery can be made, for example, at thisstage, after carrying out the above mentioned iron recovery.

With solvent extraction using countercurrent techniques, hydrochloricacid stripping and then contacting with MgO solution, thereforeprecipitating the rare earth elements in the form of hydroxide and thenconverting the products into their corresponding oxide into acalcination device.

Aluminum Recovery

This step can also be carried in various ways. For example, aluminumions can be precipitated under the form of Al(OH)₃ (for example anhydrated form of Al(OH)₃) at a pH of about 7 to about 9 or about 7.5 toabout 8.5 or about 8. Alternatively, the aluminum ions can be reactedwith an extracting agent as descried in WO2008141423.

The solution obtained from the previous step using either theprecipitation or the extraction technique is relatively clean and mainlycontains aluminum for example about 90% to about 95% or even as high asabout 90% to about 99.8% (without the alkaline-earths in the case ofprecipitation). Recovery of the latter can be carried out byliquid-liquid extraction for example by using a same hollow fibermembrane and an extracting agent that is adapted to complex at leastsubstantially selectively aluminum over other metals or residues. Forexample, bis(2,4,4-trimethylpentyl) phosphinic acid (such as the onesold under the name Cyanex™ 272) can be used as an extracting agentspecific to aluminum. For example, this extracting agent can be used ata concentration of about 20% v/v in an organic solvent such as heptane.The ratios between the aqueous phase and the organic phase can be ofabout 1:1 to about 1:3. For example, the extraction temperatures can beof about 40° C. and the pH can be maintained at about 2.5 to about 3.5.It was observed that such a technique makes it possible to extract morethan 70-90% of the aluminum. After the aluminum has been trapped in theorganic phase, it can be recovered in the form of a concentrate of Al³⁺ions by using a back extraction. For example, the reverse extraction canbe carried out at a temperature of about 40° C. with hydrochloric acid(for example at a concentration of 6 M). Under this condition, more than90% of aluminum can be recovered.

The rare earth element(s) recovery can be made, for example, at thisstage, after carrying out the above mentioned aluminum recovery.

Then, Al³⁺ can be converted into aluminum hydroxide (for example anhydrated form of Al(OH)₃) by addition of a base such as NaOH. Finally,Al(OH)₃ can be converted into alumina (alumina Al₂O₃) by r calcinatingAl(OH)₃ for example at a temperature of about 800° C. to 1200° C.

Further purification can be performed by recrystallization.

Rare Earth Elements Recovery

Rare earth elements recovery can then be made, for example, at thisstage by using any of the technology previously mentioned for doing so.For example, the at least one rare earth element contained in theresidual solutions obtained from the above-mentioned process. Forexample, the at least one rare earth element can be in low concentrationfor example at a concentration of less than about 50, about 25, 15, 10,5, 4, 3, 2 or 1 ppm in the lixiviate or leachate or a solution obtainedduring the process. The rare earth elements can be concentrated in thelatter stage of the process prior to extraction with solvent(s). It wasdemonstrated that through an internal concentration loop, concentrationcan be significantly increased (for example from 100 to 1000 times)thereby providing more effective conditions for substantiallyselectively precipitating, extracting and/or isolating at least one rareearth element.

Example 2

As a starting material a sample of clay (argillite) was obtained fromthe Grande Valleé area in Québec, Canada.

These results represent an average of 80 tests carried out from samplesof about 900 kg each. These tests were carried out by a using a processas shown in FIG. 1.

Crude clay in the freshly mined state after grinding and classificationhad the following composition:

Al₂O₃: 15%-26%;

SiO₂: 45%-50%;

Fe₂O₃: 8%-9%;

MgO: 1%-2%;

Rare earth elements: 0.04%-0.07%;

LOI: 5%-10%.

This material is thereafter leached in a two-stage procedure at 140-170°C. with 18-32 weight % HCl. The HCl solution was used in astoichiometric excess of 10-20% based on the stoichiometric quantityrequired for the removal of the acid leachable constituents of the clay.In the first leaching stage of the semi-continuous operation (step 2),the clay was contacted for 2.5 hours with required amount or certainproportion of the total amount of hydrochloric acid. After removal ofthe spent acid, the clay was contacted again with a minimum 18 weight %hydrochloric acid solution for about 1.5 hour at same temperature andpressure.

The leachate was filtered and the solid was washed with water andanalyzed using conventional analysis techniques (see step 3 of FIG. 1).Purity of obtained silica was of 95.4% and it was free of any chloridesand of HCl.

After the leaching and silica removal, the concentration of the variousmetal chlorides was:

AlCl₃: 15-20%;

FeCl₂: 4-6%;

FeCl₃: 0.5-2.0%;

MgCl₂: 0.5-2.0%;

Free HCl: 5-50 g/l

Spent acid was then crystallized using about 90 to about 98% pure dryhydrochloric acid in gas phase in two stages with less than 25 ppm ironin the aluminum chloride hexahydrate formed. The concentration of HCl insolution (aqueous phase) was about 25 to about 32% The recoveredcrystallized material (hydrate form of AlCl₃ having a minimum purity of99.8%) was then calcined at 930° C. or 1250° C., thus obtaining theα-portion of the alumina.

HCl concentration in gas phase exiting the calcination stage was havinga concentration of about 21 to about 32% by weight and was used(recycled) for crystallization of the AlCl₃ and MgCl₂. Excess ofhydrochloric acid is absorbed at the required and targeted concentrationfor the leaching steps.

Iron chloride (about 90% to about 95% in ferric form) is then sent to ahydrothermal process in view of its extraction as pure hematite (Fe₂O₃).This can be done by using the technology described in WO 2009/153321 oflow temperature hydrolysis with full heat recovery from calcining,pyrohydrolysis and leaching stage.

Before step 10 (in both processes of FIGS. 1 and 2) it was demonstratedthat about 90 to about 98% by weight of the elements (Al, Fe, Mg andrare earths elements such as (Sc, Ga, Y, Ce) found in the startingmaterial were recovered. It can be estimated that the processes forrecovering rare earth elements from an aluminum-bearing materialdisclosed in the present disclosure can be efficient for recoveringabout 90% of the rare earth elements. Thus, with respect to the examplesof processes provided in FIGS. 1 and 2, it can be estimated that theoverall yield for recovering the at least one rare earth element fromthe aluminum-bearing material would be about 80% to about 90%.

Rare earth elements can be extracted from the mother liquor of thehydrolyzer (where silica, aluminum, iron and a great portion of waterhave been removed) following pre-concentration from crystallization tothe hydrolyzer. In the form of chlorides the rare earth elements (RECl)are considerably concentrated and ready to be extracted. Rare earthelements have demonstrated to concentrate by a factor 5 to 10 in averagewithin the hydrolyzer itself on a single pass through it (without anyconcentration loop). The concentration factors obtained within thehydrolyser (single pass) were as follows:

-   -   Ce: >6    -   La: >9    -   Nd: >7    -   Y: >9

The person skilled in the art would thus clearly understand that such aconcentration could be considerably more increased when carrying out aconcentration loop.

Remaining magnesium chloride is sparged with dry and highly concentratedhydrochloric acid and then calcinated to MgO while recovering acid atits azeotropic point.

Mixed oxides containing other non-hydrolyzable components were thenundergoing a pyrohydrolysis reaction at 700-800° C. and recovered acid(15-20.2% wt.) was rerouted for example to the leaching system.

Overall Yields Obtained:

Al₂O₃: 93-95% recovery;

Fe₂O₃: 98-99.5% recovery;

Rare earth elements: 95% minimum recovery (mixture);

MgO: 96-98% recovery;

Material discarded: 0-5% maximum;

HCl global recovery: 99.75% minimum;

HCl strength as feed to leaching 15-32%;

Red mud production: none.

Example 3

A similar feed material (bauxite instead of clay) was processed as perin example 2 up to the leaching stage and revealed to be easilyleachable under the conditions established in example 2. It provided anextraction percentage of 100% for the iron and over 95% for aluminum.The process was found to be economically viable and no harmfulby-products (red mud) were generated. A rare earth elements recovery (asa mixture) of about 90 to about 95% (by weight as compared to thestarting material) was observed Samples tested had variousconcentrations of Al₂O₃ (up to 51%), Fe₂O₃ (up to 27%) and MgO (up to1.5%).

The processes of the present disclosure provide a plurality of importantadvantages and distinction over the known processes

The processes of the present disclosure can provide fully continuous andeconomical solutions that can successfully extract alumina from varioustype of minerals while providing ultra pure secondary products of highadded value including highly concentrated rare earth elements. Thetechnology described in the present disclosure can allow for aninnovative amount of total acid recovery and also for a ultra highconcentration of recovered acid. When combing it to the fact thatcombined with a semi-continuous leaching approach that favors very highextraction yields and allows a specific method of crystallization of thealuminum chloride and concentration of other value added elements suchas rare earth elements.

Specifically through the type of equipment used (for example verticalroller mill) and its specific operation, raw material grinding, dryingand classifying can be applicable to various kinds of mineral hardness(furnace slag for example), various types of humidity (up to 30%) andincoming particle sizes. The particle size established provides theadvantage, at the leaching stage, of allowing optimal contact betweenthe minerals and the acid and then allowing faster kinetics of reaction.Particles size employed reduces drastically the abrasion issue andallows for the use of a simplified metallurgy/lining when in contactwith hydrochloric acid.

A further advantage of the processes of the present disclosure is thecombined high temperature and high incoming hydrochloric acidconcentration. Combined with a semi continuous operation where the freeHCl driving force is used systematically, iron and aluminum extractionyields do respectively reach 100% and 98% in less than about 40% of thereference time of a basic batch process. Another advantage of higher HClconcentration than the concentration at azeotropic point is thepotential of capacity increase. Again a higher HCl concentration thanthe concentration of HCl at the azeotropic point and the semi-continuousapproach represent a substantial advance in the art.

Another advantage in that technique used for the mother liquorseparation from the silica after the leaching stage countercurrent wash,is that band filters provide ultra pure silica with expected purityexceeding 98%.

The crystallization of AlCl₃ into AlCl₃.6H₂O using dried, cleaned andhighly concentrated gaseous HCl as the sparging agent allows for a purealuminum chloride hexahydrate with only few parts per million of ironand other impurities. A minimal number of stages can be required toallow proper crystal growth.

The direct interconnection with the calcination of AlCl₃.6H₂O into Al₂O₃which does produce very high concentration of gas allows the exactadjustment in continuous of the HCl concentration within thecrystallizer and thus proper control of the crystal growth andcrystallization process.

The applicants have now discovered fully integrated and continuousprocesses with total hydrochloric acid recovery for the extraction ofalumina and other value added products such as rare earth elements fromvarious materials that contain aluminum (clay, bauxite, slag, red mudetc.) containing aluminum. In fact, the processes allows for theproduction of pure alumina and other value added products purified suchas purified silica, pure hematite, pure other minerals (ex: magnesiumoxide) and rare earth elements. In addition, the processes do notrequire thermal pre-treatment before the acid leach operation. Acidleach can be carried out using semi-continuous techniques with highpressure and temperature conditions and very high regeneratedhydrochloric acid concentration.

The advantage of the high temperature calcination stage, in addition forallowing to control the α-form of alumina required, is effective forproviding a concentration of hydrochloric acid in the aqueous form(>38%) that is higher than the concentration of HCl at the azeotropicpoint and thus providing a higher incoming HCl concentration to theleaching stage. The calcination stage hydrochloric acid network can beinterconnected to two (2) crystallization systems and by pressureregulation excess HCl can be being absorbed at the highest possibleaqueous concentration. The advantage of having a hexahydrate incomingfeed allows for a continuous basis to recover acid at a concentrationthat is higher than the azeotropic concentration. This HCl balance anddouble usage into three (3) common parts of the process and overazeotropic point is a substantial advance in the art.

Another advantage is the use of the incoming chemistry (ferric chloride)to the iron oxide and hydrochloric acid recovery unit where all excessheat load from any calcination part, pyrohydrolysis and leaching part isbeing recovered to preconcentrate the mother liquor in metal chloride,thus allowing, at very low temperature, the hydrolysis of the ferricchloride in the form of very pure hematite and the acid regeneration atthe same concentration than at its azeotropic point.

A further major advantage of the instant process at the ferric chloridehydrolysis step is the possibility to concentrate rare earth elements inform of chlorides at very high concentration within the hydrolyserreactor. The advantage is that the processes of the present disclosurebenefit from the various steps where gradual concentration ratios areapplied. Thus, at this stage, having the silica, the aluminum, the ironand having in equilibrium a solution close to saturation (large amountof water evaporated, no presence of free hydrochloric acid) allows fortaking rare earth elements in parts per million into the incoming feedand to concentrate them in high percentage portion directly at thehydrolyser. Purification of the specific oxides of the rare earthelements (REO) can then be performed using known techniques when inpercentage levels. The advantage is doubled here: concentration at veryhigh level of rare earth elements using integrated process stages andmost importantly the approach prevents from having the main stream (verydiluted) of spent acid after the leaching step with the risk ofcontaminating the main aluminum chloride stream and thus affectingyields in Al₂O₃. Another important improvement of the art is that on topof being fully integrated, selective removal of components allows forthe concentration of rare earth elements to relatively highconcentration (percentages).

Another advantage of the process is again a selective crystallization ofMgCl₂ through the sparging from either the alumina calcination step orthe magnesium oxide direct calcination where in both cases highlyconcentrated acid both in gaseous phase or in aqueous form are beinggenerated. As per aluminum chloride specific crystallization, the directinterconnection with the calciner, the HCl gas very high concentrationallows for exact adjustment in continuous of the crystallizer based onquality of magnesium oxide targeted. Should this process step (MgOproduction or other value added metal oxide) be required based onincoming process feed chemistry, the rare earth elements extractionpoint then be done after this additional step; the advantage being theextra concentration effect applied.

The pyrohydrolysis allows for the final conversion of any remainingchloride and the production of refined oxides that can be used (in caseof clay as starting material) as a fertilizer and allowing theprocessing of large amount of wash water from the processes with therecovery hydrochloric acid in close loop at the azeotropic point for theleaching step. The advantage of this last step is related to the factthat it does totally close the process loop in terms of acid recoveryand the insurance that no residues harmful to the environment are beinggenerated while processing any type of raw material, as previouslydescribed.

A major contribution to the art is that the proposed fully integratedprocesses of the present disclosure is really allowing, among others,the processing of bauxite in an economic way while generating no red mudor harmful residues. In addition to the fact of being applicable toother natural of raw materials (any suitable aluminum-bearing materialor aluminous ores), the fact of using hydrochloric acid total recoveryand a global concentration that is higher than the concentration at theazeotropic point (20% to 38%), the selective extraction of value addedsecondary products and compliance (while remaining highly competitive ontransformation cost) with environmental requirements, represent majoradvantages in the art.

It was thus demonstrated that the present disclosure provides fullyintegrated processes for the preparation of pure aluminum oxide using ahydrochloric acid treatment while producing high purity and high qualityproducts (minerals) and recovering rare earth elements.

The person skilled in the art will thus understand that the processes ofthe present disclosure can be used in combination with various processesfor treating aluminum-bearing materials. In fact, various differenttreatments can be carried out to the aluminum-bearing materials in theprocesses of the present disclosure including recovery of at least onerare element.

While a description was made with particular reference to the specificembodiments, it will be understood that numerous modifications theretowill appear to those skilled in the art. Accordingly, the abovedescription and accompanying drawings should be taken as specificexamples and not in a limiting sense.

What is claimed is:
 1. A process for recovering at least one rare earthelement and/or at least one rare metal selected from the groupconsisting of In, Zr, Li and Ga from at least one material, said processcomprising: leaching said at least one material with HCl so as to obtaina leachate comprising a first metal ion, a second metal ion, said atleast one rare earth element and/or said at least one rare metalselected from the group consisting of In, Zr, Li and Ga, and a solid,and separating said leachate from said solid; substantially selectivelyremoving said first metal ion from said leachate, thereby obtaining acomposition comprising said second metal ion and said at least one rareearth element and/or said at least one rare metal selected from thegroup consisting of In, Zr, Li and Ga; substantially selectivelyremoving at least partially said second metal ion from said composition,thereby obtaining a liquor comprising said at least one rare earthelement and/or said at least one rare metal selected from the groupconsisting of In, Zr, Li and Ga; and substantially selectively removingsaid at least one rare earth element and/or at least one rare metalselected from the group consisting of In, Zr, Li and Ga from saidliquor, wherein said liquor comprises GaCl₃ and is reacted with a firstextracting agent in order to substantially selectively extract GaCl₃therefrom, thereby obtaining a Ga-free solution and an extracted galliumsolution, and separating said solutions from one another.
 2. The processof claim 1, wherein said first metal ion is substantially selectivelyremoved from said leachate by substantially selectively precipitating itfrom said leachate and removing it therefrom by carrying out asolid-liquid separation.
 3. The process of claim 2, wherein said atleast one rare earth element and/or said at least one rare metalselected from the group consisting of In, Zr, Li and Ga is substantiallyselectively precipitated, extracted and/or isolated from said liquor bymeans of a liquid-liquid extraction.
 4. The process of claim 1, whereinsaid first metal ion is at least one aluminum ion and is substantiallyselectively removed from said leachate by substantially selectivelyprecipitating it under the form of AlCl₃ and removing it therefrom bycarrying out a solid-liquid separation.
 5. The process of claim 1,wherein said composition comprises HCl, said second metal ion, and saidat least one rare earth element and/or said at least one rare metalselected from the group consisting of In, Zr, Li and Ga.
 6. The processof claim 1, wherein said extracted GaCl₃ is then precipitated and thenconverted into Ga₂O₃.
 7. The process of claim 1, wherein the Ga-freesolution is then reacted with another an extracting agent in order tosubstantially selectively extract cerium therefrom, thereby obtaining aCe-free solution and an extracted cerium solution, and separating saidsolutions from one another.
 8. The process of claim 7, wherein saidcerium in said Ga-free solution is in the form of CeCl₃.
 9. The processof claim 8, further comprising reacting the Ce-free solution with afurther extracting agent in order to substantially selectively extractscandium therefrom, thereby obtaining a Sc-free solution and anextracted scandium solution, and separating said solutions from oneanother.
 10. The process of claim 9, further comprising reacting theSc-free solution with still a further extracting agent in order tosubstantially selectively extract samarium, europium or a mixturethereof, thereby obtaining at least one of a Sm-free solution andEu-free solution; and at least one of an extracted samarium and europiumsolution, and separating said solutions from one another.
 11. Theprocess of claim 10, further comprising reacting the Sm-free solutionand/or Eu-free solution with still another extracting agent in order tosubstantially selectively extract gadolinium, thereby obtaining aGd-free solution and an extracted gadolinium solution, and separatingsaid solutions from one another.
 12. The process of claim 11, furthercomprising reacting the Gd-free solution with yet another extractingagent in order to substantially selectively extract yttrium, therebyobtaining a Y-free solution and an extracted yttrium solution, andseparating said solutions from one another.
 13. The process of claim 12,further comprising reacting the Y-free solution with still yet anotherextracting agent in order to substantially selectively extractdysprosium and/or erbium, thereby obtaining a Dy-free solution and/or anEr-free solution and an extracted dysprosium and/or erbium solution, andseparating said solutions from one another.
 14. The process of claim 1,wherein said first extracting agent is tri-butyl phosphate in kerosene.15. The process of claim 1, wherein said Ga-free solution is reactedwith a precipitating agent for precipitating at least one rare earthelement present in said Ga-free solution, thereby obtaining aprecipitate containing said at least one rare earth element andrecovering said precipitate via a solid-liquid separation.
 16. Theprocess of claim 1, wherein said at least one rare earth element issubstantially selectively removed by means of a liquid-liquidextraction.
 17. The process of claim 1, wherein said at least one rareelement is selected from the group consisting of scandium, gallium,yttrium and cerium and said at least one rare metal selected from thegroup consisting of In, Zr, Li and Ga is gallium.
 18. The process ofclaim 1, wherein said at least one rare earth element is scandium.
 19. Aprocess for recovering at least one rare earth element and/or at leastone rare metal selected from the group consisting of In, Zr, Li and Gafrom at least one material, said process comprising: leaching said atleast one material with HCl so as to obtain a leachate comprising afirst metal ion, a second metal ion, said at least one rare earthelement and/or said at least one rare metal selected from the croupconsisting of In, Zr, Li and Ga, and a solid, and separating saidleachate from said solid; substantially selectively removing said firstmetal ion from said leachate, thereby obtaining a composition comprisingsaid second metal ion and said at least one rare earth element and/orsaid at least one rare metal selected from the group consisting of In,Zr, Li and Ga; substantially selectively removing at least partiallysaid second metal ion from said composition, thereby obtaining a liquorcomprising said at least one rare earth element and/or said at least onerare metal selected from the group consisting of In, Zr, Li and Ga;substantially selectively removing said at least one rare earth elementand/or said at least one rare metal selected from the group consistingof In, Zr, Li and Ga from said liquor, wherein said liquor is reactedwith a first extracting agent in order to substantially selectivelyextract gallium therefrom, thereby obtaining a Ga-free solution and anextracted gallium solution, and separating said solutions from oneanother; and reacting said Ga-free solution with a precipitating agentfor precipitating at least one rare earth element present in saidGa-free solution, thereby obtaining a precipitate containing said atleast one rare earth element and recovering said precipitate via asolid-liquid separation.
 20. A process for recovering at least one rareearth element and/or at least one rare metal selected from the groupconsisting of In, Zr, Li and Ga from at least one material, said processcomprising: leaching said at least one material with HCl so as to obtaina leachate comprising a first metal ion, a second metal ion, said atleast one rare earth element and/or said at least one rare metalselected from the group consisting of In, Zr, Li and Ga, and a solid,and separating said leachate from said solid; substantially selectivelyremoving said first metal ion from said leachate, thereby obtaining acomposition comprising said second metal ion and said at least one rareearth element and/or said at least one rare metal selected from thegroup consisting of In, Zr, Li and Ga; substantially selectivelyremoving at least partially said second metal ion from said composition,thereby obtaining a liquor comprising said at least one rare earthelement and/or said at least one rare metal selected from the groupconsisting of In, Zr, Li and Ga, wherein said second metal ion is atleast one iron ion and is substantially selectively removed from saidcomposition by carrying out an hydrolysis so as to convert said at leastone iron ion into Fe₂O₃ and removing said Fe₂O₃ from said composition bycarrying out a solid-liquid separation, thereby obtaining said liquorcomprising said at least one rare earth element and/or said at least onerare metal selected from the group consisting of In, Zr, Li and Ga fromsaid liquor; and substantially selectively removing said at least onerare earth element and/or at least one rare metal selected from thegroup consisting of In, Zr, Li and Ga from said liquor.